1. Field of the Invention
The present invention relates to a numerical control device, and more particularly to a numerical control device for presenting information for shortening a stopping time of a drive shaft in a machining process based on a machining program.
2. Description of the Related Art
In machining of a workpiece using a machining tool, a shorter cycle time of a series of a machining process is required to improve productivity. The cycle time mainly consists of operating time in which a drive shaft of a machining tool is operated and stop time in which all drive shafts are stopped. It is important for a shorter cycle time, to first consider shortening of a stopping time in which all drive shafts are stopped, since shortened operating time in which a drive shaft of a machining tool is operated sometimes causes deterioration in machining accuracy.
As a conventional art for supporting analysis of machining process, Japanese Patent Laid-Open No. 2011-039708 discloses a technique in which, a reference value and dispersion of the cycle time are obtained from sampling signals of a plurality of times of machining, a threshold value corresponding to variation of sampling data is set by use of a value of the dispersion, failure occurrence is automatically detected using the reference value and the threshold value while relationship between sampling data and block number of machining program is displayed to be grasped. Japanese Patent Laid-Open No. 2010-092405 discloses a numerical control device which associates a time chart of a machining load acquired from time-series data of the machining load with a machining program and displays them on the same screen.
The techniques disclosed in the conventional arts are useful to some extent for detecting and analyzing a failure condition generated during a machining. However, the techniques are not useful for analyzing reduction of stopping time since it is impossible to detect stopping time of a drive shaft without occurrence of failure, such as waiting time for spindle speed to reach a preset value, in-position check in which it is determined shaft position is within a preset range.
It is necessary for improvement of stopping state of a drive shaft, to specify a stopping point of a drive shaft of a machining tool and a stopping factor and examine information of parameter setting, change of program or the like for reducing stopping time based on the stopping factor. However, there is a problem that the examination takes long time or information to reduce the stopping time is not found even when the examination is executed.